Xml 这个${..}对ant中的变量有什么作用？

我正在尝试用java构建一个应用程序，但遇到一个错误，错误是：

/home/user/Documents/Installation\u Files/csa/build2/rtiperftest.1.1b/perftest\u java/build.xml:97： 执行失败：java.io.IOException:无法运行程序 “/home/user/Documents/Installation_Files/csa/build2/rtiperftest.1.1b/${env.NDDSHOME}/scripts/rtidsgen” （在目录中） “/home/user/Documents/Installation_Files/csa/build2/rtiperftest.1.1b”）： 错误=2，没有这样的文件或目录

env.NDDSHOME是否是需要设置的环境变量

在build.xml文件中，我还看到${rtidds.rtidsgen}、${rtidds.home}、${script.suffix}和其他语法为${…}的文件。这是什么意思？这些都是在环境变量中定义的吗

以下是build.xml文件供参考：

<?xml version="1.0" encoding="UTF-8"?>
<!-- $Id: build.xml 2570 2009-05-28 14:42:37Z elaine $ Copyright 2006,
Real-Time Innovations. All rights reserved. No duplications, whole or
partial, manual or electronic, may be made without express written
permission. Any such copies, or revisions thereof, must display this
notice unaltered. This code contains trade secrets of Real-Time
Innovations, Inc. modification history:
=====================
17oct08,rbw Reorganized source files to make it easier to ship test
implementations separately 08oct08,rbw Refactored DDS dependencies to
com.rti.perftest.impl.PerfTestLauncher 20jun08,rbw javac path changes
23may08,rbw Enable preprocessor when running rtiddsgen to enable key
support 30apr08,rbw Fixed deletion order when cleaning 03apr08,rbw
Fail build when code gen fails 02apr08,rbw Created
========================================================================== -->
<project basedir=".." default="default" name="PerfTest">
  <!-- ===================================================================== -->
  <!-- End of $Id: build.xml 2570 2009-05-28 14:42:37Z elaine $ -->
  <description> A combined throughput and latency test for RTI Data Distribution Service in Java. </description>
  <!-- ================================================================= -->
  <!-- Public Targets -->
  <!-- ================================================================= -->
  <target name="default" description="Build a JAR file containing the test" depends="build-jar">
  </target>
  <target name="clean" description="Delete compiled code">
    <delete file="${jar.out.file}"/>
    <delete dir="${javac.out.dir}"/>
  </target>
  <!-- ================================================================= -->
  <!-- Internal Targets -->
  <!-- ================================================================= -->
  <target name="build-jar" depends="compile">
    <echo message="Building PerfTest JAR: ${jar.out.file}"/>
    <echo message="...containing classes: ${javac.out.dir}"/>
    <mkdir dir="${jar.out.dir}"/>
    <jar basedir="${javac.out.dir}" update="false" index="true" duplicate="fail" destfile="${jar.out.file}">
      <fileset dir="." includes="**/*.class"/>
      <manifest>
        <attribute name="Main-Class" value="com.rti.perftest.ddsimpl.PerfTestLauncher"/>
      </manifest>
    </jar>
  </target>
  <target name="compile" depends="generate">
    <echo message="Compiling PerfTest in dir: ${javac.out.dir}"/>
    <echo message="...using RTI DDS JAR file: ${rtidds.jar}"/>
    <mkdir dir="${javac.out.dir}"/>
    <javac target="1.5" optimize="${javac.optimize}" deprecation="${javac.deprecation}" debug="${javac.debug}" destdir="${javac.out.dir}" srcdir=".">
      <include name="perftest_java/**/*.java"/>
      <include name="perftest_java_util/**/*.java"/>
      <classpath>
        <pathelement path="${rtidds.jar}"/>
      </classpath>
    </javac>
  </target>
  <target name="generate" depends="properties">
    <echo message="Generating code with: ${rtidds.rtiddsgen} ${env.RTIDDSGEN_PREPROCESSOR} "/>
    <exec failonerror="true" failifexecutionfails="true" executable="${rtidds.rtiddsgen}">
      <arg line="-d perftest_java"/>
      <arg line="-language Java"/>
      <arg line="-package com.rti.perftest.gen"/>
      <arg line="-replace"/>
      <arg line="${env.RTIDDSGEN_PREPROCESSOR}"/>
      <arg file="idl/test.idl"/>
    </exec>
  </target>
  <target name="properties">
    <property environment="env"/>
    <property name="rtidds.home" location="${env.NDDSHOME}"/>
    <property name="rtidds.jar" location="${rtidds.home}/class/nddsjava.jar"/>
    <property name="env.RTIDDSGEN_PREPROCESSOR" value=""/>
    <condition value=".bat" else="" property="script.suffix">
      <os family="Windows"/>
    </condition>
    <property name="rtidds.rtiddsgen" location="${rtidds.home}/scripts/rtiddsgen${script.suffix}"/>
  </target>
</project>

Java中RTI数据分发服务的吞吐量和延迟组合测试。

在ant中，

${property\u name}

计算为绑定到名为

property\u name

的属性的值

语句意味着将环境值绑定到

环境。

。其他

${}

构造（不带

env.

前缀）指其他非环境属性，通常在生成文件或外部属性文件中设置

因此，错误消息表明

NDDSHOME

环境变量的设置有问题

${env.NDDSHOME}

用于设置

rtidds.home

，该设置用于指定

rtidds.jar

的位置，并在将

rtidds.rtidsgen

指定为

${rtidds.home}/scripts/rtidsgen${script script.suffix}

中发挥作用。脚本可能希望您为本地安装正确设置此选项